Study of the effect of δ phase on hydrogen embrittlement of Inconel 718 by notch tensile tests

This article describes the effect of δ phase on the hydrogen embrittlement (HE) sensitivity of Inconel 718 conducted by notch tensile tests. Notch tensile specimens were subjected to proper heat treatment to produce various precipitation morphologies of δ phase. Hydrogen was charged into the tensile specimens before tensile tests via a cathodic charging process. The loss of notch tensile strength (NTS) due to hydrogen charging has been used as a criterion to evaluate the hydrogen embrittlement sensitivity. The study suggests that δ phase has deleterious effect on NTS. Fracture origins of hydrogen-charged specimens locate near the notch surfaces. The loss of NTS caused by hydrogen charging can be greatly decreased by dissolving δ. δ-free Inconel 718 has been proposed for applications in hydrogen environments.